Why a real-estate radon test can't use a basic kit

ANSI/AARST's current testing protocol (the MAH standard, most recently updated in 2023) sets specific device requirements for a real-estate transaction test, not just a minimum radon reading: the device must log hourly, detect and report tampering, and carry an annual third-party calibration certificate. Placement is specified too — at least 12 inches from exterior walls, 36 inches from windows, 20 inches above the floor, in the lowest livable area — and closed-building conditions have to hold for 12 hours before the device goes in and through the full 48-hour minimum test. A single-use charcoal kit mailed to a lab can't produce any of that: no hourly log, no tamper record, nothing to hand a buyer's agent who asks how the number was verified.

What a professional-grade monitor adds

A continuous monitor built for this work needs three things a consumer test kit doesn't: hourly-resolution logging over the full test window, a tamper or tilt sensor that flags if the device was moved, and a calibration record against a reference instrument in an accredited lab. It also has to survive being used on dozens of jobs a year rather than once — the cost that matters for a working inspector isn't the sticker price, it's the cost per job over a device that gets reused instead of mailed off and replaced.

Where this site's radon numbers fit in

RadonZoneCheck's own EPA zone rating is exactly what AARST's protocol says it can't replace — a county-level average, not a device-verified reading of one house. See what a zone rating does and doesn't tell you for the same distinction from the homeowner side. A professional testing a specific property, in a Los Angeles County, CA-sized market or a smaller one, still needs the device-level protocol above regardless of which zone the county falls in.

Airthings Corentium Pro

The Corentium Pro is AARST-NRPP and C-NRPP certified, stores up to 5 years of hourly-resolution data, and includes tilt/tamper detection — the three protocol requirements above, from one reusable device. See it at Airthings. Affiliate link: RadonZoneCheck earns a commission on a qualifying purchase there, at no extra cost to you. Code RADONZONE-10OFF takes 10% off at checkout.

Where to go next

See the range this plays out across: Loving County, TX, Logan County, KY, Middlesex County, MA.

How RadonZoneCheck Reports Your County's Radon Zone · What Your County's Radon Zone Actually Means (and Doesn't)